The invention is directed to improvements in fuel injection pumps having an anti-bucking adjustment feature.
Because of the elastic suspension of the engine and chassis, a motor vehicle is a structure capable of vibrating, and if disturbed it can be made to vibrate in a variably damped manner. Such disturbances may include a sudden increase in the fuel quantity varying abnormally the fuel metering rate at which the combustion chambers of the engine are supplied, or a sudden increase in running resistance moment in response to external causes, such as a pothole in the road. The vibrations that are perceived as unpleasant, for example in the form of changes in rpm or of relative movements between the engine and the vehicle body, are normally in the range between 1 and 8 Hz, most likely approximately 5 Hz, and are called "bucking". The result is longitudinal vibrations, in the direction the vehicle is moving, which are exacerbated by the driver's reaction at the gas pedal and are promoted by soft vehicle suspensions. The determining factor is above all the phase displacement between the incident rpm or vehicle speed and the fuel metering quantity.
To overcome bucking, various devices have beer developed, such as that disclosed in German Offenlegungsschrift No. 33 43 854, for phase-displaced imposition of a correction signal upon a control variable for setting the fuel quantity, the control variable being calculated in accordance with operating parameters. In this case the intervention is performed solely in the context of an electronic governor, with a corrected control variable for the electromagnetically actuated supply quantity adjusting device appearing at the output of the governor; in calculating the control variable, both the operating state of the engine at the time and vehicle behavior, or bucking, are taken into account.
From German patent application No. P 34 27 224, U.S. application Ser. No. 023,946, filed 9-26-8, which is not a prior publication to this invention, instead of making an electronic intervention, it is also known to attain damping of bucking in a mechanically governed fuel injection pump by active variation of the fuel injection quantity, in particular to improve the phase location. In this kind of fuel injection pump, the engine is elastically supported in the vehicle body, and the fuel injection pump is connected to the engine. A connection, containing a differentiation device, with a quantity adjusting device of the fuel injection pump is pivotably connected to the vehicle body, functioning such that when there are rapid relative movements between the engine and the body, correspondingly rapid corrections of the fuel injection quantity are provided. Only the differentiated signal is used for corrective adjustment, however, in such a way that no adjustment of the fuel injection quantity takes place when the relative engine movements are slow.
In such an apparatus, the correction engages the governor lever to which the governor spring of a mechanical speed governor is attached, and which serves to indicate the desired torque or to set an rpm. In another version, the intervention is done hydraulically, via the adjusting member of a centrifugal speed governor. Both interventions have the disadvantage on the one hand acting indirectly, via interposed elastic members, upon the fuel supply quantity, adjusting device, and on the other hand of being affected by operating parameters, that is, by the random variation in load.